The Clinical Core will complete the Core Assessment Battery on the initial group of 377 subjects recruited through the previous funding cycle of the program project and recruit a new group of Tourette's syndrome (TS), obsessive-compulsive disorder (OCD), and attention deficit hyperactivity disorder (ADHD) subjects and matched community controls to participate in the proposed genetic, in vivo neuroimaging, neurobiological mechanisms, and treatment studies. To this end the core will develop rosters of eligible TS, OCD, and ADHD cases and controls, using clinical, community, and advocacy group resources, and will implement and monitor a Revised Minority Outreach Program to ensure optimal participation of women and minorities. The Clinical Core also has the responsibility to maintain and administer a Core Assessment Battery (CAB) for all subjects. A key element of this task is to train and monitor assessors in the reliable administration of the CAB. After ensuring the accuracy and completeness of the data acquired, the Clinical Core will transfer all data obtained to the Data Analytic Core for data entry. The core is also charged to ensure adherence of clinical studies to protocol designs and compliance with regulations involving human subjects. Finally, the investigators in the core will analyze data pertaining to the phenomenology and natural history of TS, OCD, and ADHD to refine clinical phenotypes and assessment procedures. These aims will be achieved through weekly meetings of the core and the daily efforts of the core personnel.